minEffect.SLR			Calculate minimal detectable slope given
				sample size and power for
				simple linear regression
minEffect.VSMc			Calculate minimal detectable mediation effect 
				given sample size and power for
				Vittinghoff and McCulloch's (2009) test
powerMediation.Sobel		Calculate power for testing mediation effect 
				based on Sobel's test
powerMediation.VSMc		Calculate power for testing mediation 
				effect based on Vittinghoff and McCulloch's 
				(2009) method 
power.SLR			Calculate power for testing slope
				for simple linear regression
power.SLR.rho			Calculate power for testing slope
				for simple linear regression based on R2
ssMediation.Sobel		Calculate sample size for testing mediation 
				effect based on Sobel's test
ssMediation.VSMc		Calculate sample size for testing mediation 
				effect based on Vittinghoff and McCulloch's 
				(2009) method 
ss.SLR				Calculate sample size for testing slope
				for simple linear regression
ss.SLR.rho			Calculate sample size for testing slope
				for simple linear regression based on R2
testMediation.Sobel		Calculate p-value and confidence interval
				for testing mediation effect 
				based on Sobel's test
